In recent years, better mine lighting has become a requirement. However, the combination of conditions mine lighting must meet is unique. Such lighting as was immediately available when Federal legislation mandated improved lighting has not been conceived with as much and as broad attention as thereafter has come to bear on this part of technology.
In the course of preparing this disclosure of the invention, the inventor has become aware of the following prior U.S. patents.
The following show lamp housings that present lenses at an angle in a generally triangular arrangement.
U.S. Pat. No. Des.35,857; Pause; Apr. 8, 1902
U.S. Pat. No. Des.60,322; Damm; Feb. 7, 1922
U.S. Pat. No. Des.71,571; Wilhelm; Nov. 30, 1926
U.S. Pat. No. 2,018,788; Johnson; Oct. 29, 1935
U.S. Pat. No. 2,413,381; Rylsky; Dec. 31, 1946
U.S. Pat. No. 2,752,480; Priebe; June 26, 1956